Abstract: Polyoxymethylene is obtained in a stabilized form by polymerizing formaldehyde in a liquid organic diluent containing in a dispersed form a catalyst-stabilizer consisting of a polylactamic polymer carrying a terminal ionic couple on its macromolecular chain, said catalyst-stabilizer being present in an amount of from 0.1 to 5 parts by weight for each 100 parts of polyoxymethylene.

Abstract: Process for the stabilization of polyacetal resins having terminal hydroxyl groups, which comprises reacting a reagent capable of etherifying the hydroxyl groups with the polyacetal resins suspended in a reaction medium that is liquid under the conditions used, the said reaction medium consisting of at least one substance that is a solvent for the polymer and at least one substance that is a non-solvent for the polymer, the said solvent and non-solvent substances being completely miscible at the reaction temperatures but immiscible or partly miscible at temperature substantially lower than the reaction temperatures, and carrying out the operation in the presence of catalytic quantities of one or more compounds selected from the groups consisting ofA. strong or medium-strong mineral acids whose acid dissociation constant or first acid dissociation constant is higher than 10.sup..sup.-7 ;B. strong or medium-strong oganic acids whose acid dissociation constant is higher than 10.sup..sup.-6 ;C.

Abstract: A novel block copolymer HO--D--A--B--D--H, whereinA is a polylactonic block of recurring units ##EQU1## B is a polylactamic block of recurring units ##EQU2## C is a polyoxymethylene block of recurring units--CH.sub.2 O--is prepared by catalytic polymerization of at least one lactone ##EQU3## with at least one lactam ##EQU4## wherein: PM.sub.1 and PM.sub.2 are polymethylene linear chains having from 2 to 13 and 3 to 13 carbon atoms, respectively, and being either non-substituted or having at least one hydrogen atom replaced by an alkyl, aryl, alkylaryl or cycloalkyl radical, and reaction of the resulting A-B copolymer with monomeric formaldehyde.The block copolymer HO--D--A--B--D--H having a preponderant percentage in blocks A, B or D, respectively, behaves as a polylactone, polylactam or polyformaldehyde, respectively, having improved properties.

Abstract: Polyformaldehyde is prepared by feeding anhydrous formaldehyde to a reaction medium containing a liquid organic diluent non-solvent for the polyformaldehyde and non-reactive towards the other constituents of the reaction medium, and containing in a dispersed form a copolymer A-B, whereinA is a polylactonic block of recurring units ##EQU1## B is a polylactamic block of recurring units ##EQU2## wherein PM.sub.1 and PM.sub.2 are linear polymethylene chains having from 2 to 13 and 3 to 13 carbon atoms, respectively.

Abstract: A stabilized polymeric composition comprising an acetal polymer and as stabilizer a copolymer R--D--A--B--D--R, in which:A is a block of recurring units: ##EQU1## B is a block of recurring units: ##EQU2## D is a block of recurring units: ##EQU3## R is an ester, ether or urethane group wherein PM.sub.1 and PM.sub.2 are linear polymethylene chains having 2 to 13 and 3 to 13 carbon atoms, respectively, non substituted or having at least one hydrogen atom replaced by an alkyl, aryl, alkylaryl or cycloalkyl radical; the said stabilizer being used in a proportion of from 0.02 to 12 parts by weight to 100 parts by weight an acetal polymer.

Abstract: A process for purifying a polymerisable monomer selected from the group consisting of cyclic ethers, hydrocarbon olefins, vinyl compounds, aldehydes, lactams of the formula: ##EQU1## wherein x is an integer from 3 to 13 and lactones of the formula: ##EQU2## wherein n is an integer of from 1 to 4 and wherein R represents an hydrogen atom, an alkyl group or an aryl group; said process comprising contacting a liquid consisting of said monomer at a temperature of not greater than 130.degree. centigrade and at a pressure sufficient to keep said monomer in liquid form, with a solid absorbent consisting essentially of a porous reticulated macromolecular alkali metal or alkaline earth metal salt of a cationic exchange resin containing carboxylic, sulfonic or phosphoric acid groups, said cationic exchange resin having a specific surface area of at least one square meter per gram and a pore diameter of from 10.sup.1.3 to 10.sup.5 angstroms and recovering the purified monomer.